Grease



Patented Feb. 2,1945

T. OFFICE GREASE Fred E. Woodward and Jerome W. Arkis,

Davenport, Iowa No Drawing. Application July 8, 1942, Serial No. 450,184

2 Claims. ((31. 252-37) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) -more particularly to an improved grease, stabilized against deterioration in the presence of oxygen.

Prior art greases heretofore employed in the recoil mechanisms of modern artillery pieces, rapidly break down when subjected to an oxygen-containing atmosphere, particularly in .the presence of copper or alloys thereof. With such prior art greases, copper or an alloy thereof appears to act asa decomposition accelerator or catalyst, greatly increasing the rate of breakdown of the grease in the presence of oxygen. Thus it has been found, using the Norma-Hoffmann accelerated stability test for lubricating greases (A. S. T. M. Preprint No. 94, 1938), that the induction period of prior aluminum base r ecoil greases drops from some 960+ hours, when the test is carried out in glass dishes without a catalyst, to perhaps 48 hours or lower when the test is performed in the presence of a catalyst comprising naval brass. In view of the fact that recoil mechanisms usually contain copper or alloys thereof such as brass, it is apparent that an improved stabilizer is required for recoil greases so that such greases may be made proof against oxidative deterioration in the presence of coppercontaining metals.

The object of the present invention is to provide a grease characterized by increased stability to oxygen in the presence of copper or copper alloys such as brass.

A' further object is to provide a meansfor increasing the oxygen induction period for aluminum base recoil greases when tested by the .Norma-Hofimann accelerated stability test in the presence of copper containing catalysts. Another object is to provide a method of stabilizing recoil greases of all types, against oxidative deterioration in the presence of copper or copper containing'metals.

Still another object is the provision of a new and improved grease stabilizer which greatly in-v creases the stability of greases to the destructive effect of oxygen in the presence of a copper-containing catalyst, which stabilizer does not impair the other desirable properties of the grease.

Other objects and advantages of the present invention will appear as the invention is hereinafter more particularly described.

We have'found that the foregoing objects may be accomplished in accordance with the present invention, one aspect of which involves the incorporation in the recoil grease, of a small percentage of a stabilizer selected from the group consisting of:

(a) Aryl-substituted, naphthyl amines, such as phenyl beta naphthyl amine;

(b) Aryl-substituted arylene diamines, such as I diphenyl para phenylene diamine; or

(c) Alkoxy diaryl amines, such as diparamethoxydiphenylamine.

The foregoing stabilizers may be used singly, or in combination with each other, or in combination with other compounds, as desired.

In carrying out a preferred embodiment of the present invention, the herein disclosed stabilizers, either singly or in combination, are incorporated at any suitable step in the compounding of the grease. Thus, for example, the improved stabilized grease of the present invention may be compounded by first incorporating a conventional grease-base soap (for example, aluminum stearate, oleate and/or palmitate) in a suitable grease-base oil. After the soap and oil have been suitably mixed, a small percentage, for example 1% (based on the weight of the soap and oil) of the inhibitor is added to the grease-base. In some instances it may also be desirable to incorporate a small percentage of a free fatty acid, such as stearic acid, in order to overcome any tendency of the ultimate grease, to bleed.

After the components have been thoroughly mixed, the grease is maintained at an elevated temperature in order to permit the escape of any occluded air. When the air has been completely removed, the grease is allowed to chill very slowly, thereby insuring a grease having a proper jell and consistency.

In order more clearly to disclose the nature of the present invention, a preferred embodiment thereof will hereinafter be described. In this ex-' of the appended claims, inasmuch as any of the foregoing stabilizers may be substituted for the (usually a a len added to the oil and the mixture thoroughly Y gitated in the cold in order to wet the soap 1th the oil. Thereafter the oil and soap may a permitted to stand. However, if preferred, the

ixture may be heated immediately to approxiately 325-359 F., with constant agitation, in orar to melt the soap. When the soap has been )mpletely melted and thoroughly incorporated l the oil, 1% of phenyl beta-naphthylamine is virred into the grease. Preferably there is also lcorporated at this time approximately 0.2% of ac fatty acid, such as stearic acid, the particlar amount selected being sufllcient to insure mat the ultimate grease will not be alkaline in aaction.

The agitation of the mixture iscontinued for bout half an hour after whichthe material is rawn or run into shallow containers which are hen placed in an oven heated to approximately 50. The containers are allowed to remain in he oven for approximately 24 hours in order to llow occluded air to escape. The initial temlerature of 350 F. may be very gradually reduced Iver the twenty-four hour period, or the grease nay be held at a constant temperature for the nitial twenty-four hour period and thereafter iermitted to chill very slowly. The latter method if cooling is usually preferable inasmuch as it nsures a grease which has a proper ,iell and vhich also will not show any tendency to bleed.

In some instances, it may be desirable to add in the table (I. P.=413).

lthel stabilizers in addition to the phenyl betaiaphthylamine employed in the foregoing eximple. Thus for example, the stabilizer may :onsist of two parts by weight phenyl betaiaphthylamine, one part by weight dlparanethoxydiphenylamine and one part of diphenvlparaphenylene diamine, this mixture being :mployed in the greaseto the extent of'l% by weight. In other instances it may be desirable 50 use the various stabilizers individually or in various proportions. Although we have discovered that the employment of a stabilizer comprising substantially one per cent (1%) by weightof the total weight of the grease provides optimum antioxidant performance from the economic standpoint it will be apparent that other percentages of stabilizer may also be employed, the antioxidant effect thereof being dependent to a certain extent upon the quantity or proportion used.

In order to establish the stability of greases prepared in accordance with the present invention, experiments were conducted using the Norma-Hofimann accelerated stability test for lubricating greases. This procedure included the loading of various greases, prepared under identical conditions, in a Norma-Hofimann bomb.

Each dish of the bomb contained a naval brass catalyst having a surface area of 0.756 square inch. The subsequent details of the tests were similar to those set forth in the A. T. M. Preprint mentioned above. The results are indicated in the table.

quently show It will thus be seen l A-phenyl alpha naghth lamine.

1 B-phenyl beta nap thy amine.

3 C--diparam ethoxydiphenylamine.

4 D-dipbenyl para phenylene diamine.

As will be apparent from the induction periods noted in the foregoing table, a grease-containing phenyl beta naphthylamine is substantially more stable under the conditions of the test than a grease containing the alpha position isomer (384 compared with189). Further improvement was noted when the other inhibitors were incorporated along with the phenyl beta naphthylamine, as indicated by the last example The grease represented by sample .A" is, in turn, far more stable than the same grease without the phenyl alpha naphthylamine, as indicated by the factthat a similar grease containing no inhibitor will frean induction period below 30, and greases containing the usual commercial "metal deactivaters do not show any measurably greater stability under the conditions of the test. that the incorporation of a very small percentage of ,the improved stabilizers of the present invention results in an entirely unexpected (and indeed, inexplicable) enhancement in stability of greases under the conditions of the Norma-Hoffmann test, when carried out in the presence of a copper-containing metal.

In the foregoing detailed description it will be apparent to those skilled-in the art that many variations may be made without departing from the spirit and scope of the present invention.

Thus for example, although the invention has and a stabilizer consisting substantially of a mixture of about 25% diparamethoxydiphenylamine, about 25% diphenylparaphenylene diamine and about 50% phenyl beta naphthylamine.

2. A grease comprising a metal-soap, an oil, and an antioxidant stabilizer comprising substantially one per cent (1%) byyeight of said grease, said stabilizer comprising substantially a mixture of about 25% dipara methoxy-diphenylamine, about 25% diphenyl paraphenylene diamine and about 50% phenyl betanaphthylamine, and wherein said soap comprises an aluminum salt of a long chain fatty acid.

FRED E. woonwann.

annom'. w. ARKIS.

Y CERTIFICATE 9F CORRECTION. Patent No. 2,569,70 February 20, 1915.

FRED E. WOODWARD, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column, line 15, for "525-359 F." read 325-550 F.-; and that the said Letters Patent should be read wifiz this correction therein that the same may confomto the record of the case in the Patent ffice.

Signed and sealed this 19th day of June, A. D. 1915.

Leslie Frazer (Seal) A ting Commissioner of Patents. 

